If it's a commercial decision to stop services in their own right, and then subsequently codeshare, what's the problem?

Airlines do it all the time.

The ACCC will not permit codeshares if it lessens competition, airlines do it all the time but it still needs to be authorised by the ACCC. Case in point was the recent SQ VA authorisation getting a shorter approval than sought by the airlines.

It's unlikely to be a code share - unless VA decides to put its code on a QLink service, which it won't, then there are no other scheduled carriers on any of those routes. What is more likely is that VA will wet lease more frames from Alliance (or Jetgo, if they had any sense, for the likes of Bundy) to operate these routes on its behalf, a la Emerald, Mt Isa & Cloncurry. In that case, the ACCC would be overreaching significantly if it had any involvement whatsoever.

According to media reports out of Central Qld over the last couple of hours, it's confirmed that Alliance Airlines F70s will take over VA operations on Brisbane to Bundaberg, Gladstone, Moranbah & Port Macquarie. I would think that might also mean some SYD-PQQ services might move over to the F70s, but perhaps not and the services will be retimed?